(Reuters) - A California court on Wednesday rejected an appeal by a former Stanford University swimmer who was found guilty of sexual assault and served a sentence that many say was too lenient.

FILE PHOTO: Brock Turner, the former Stanford swimmer convicted of sexually assaulting an unconscious woman, leaves the Santa Clara County Jail in San Jose, California, U.S. September 2, 2016. REUTERS/Stephen Lam

Brock Turner, then 19, was arrested in 2015 after two fellow students at the Northern California university saw him outside a fraternity house on top of an unconscious woman.

He was convicted of sexual assault the following year and sentenced to six months, a sentence criticized as too lenient by political leaders, residents and social media users.

FILE PHOTO: Former Stanford student Brock Turner who was sentenced to six months in county jail for the sexual assault of an unconscious and intoxicated woman is shown in this Santa Clara County Sheriff's booking photo taken January 18, 2015, and received June 7, 2016. Santa Clara County Sheriff's Department/Handout via REUTERS/File Photo

Turner was released early for good behavior after serving three months. He had to register as a sex offender in his home state of Ohio, after leaving Stanford.

In December, Turner appealed, asking for the conviction to be overturned or a new trial, based on a lack of sufficient evidence.

The Sixth District Court of Appeal in California ruled that the “argument lacks merit” and that there was “substantial evidence” to convict Turner, a court document showed.

The sentence Santa Clara County Superior Court Judge Aaron Persky gave Turner stoked intense debate about rape on U.S. college campuses. Voters recalled Persky in June because of the sentence.

In response to the Turner case, California lawmakers passed legislation to broaden the state’s legal definition of rape and mandate prison if the victim was unconscious.